How to get a field mouse lost?
May 19, 2011 9:02 PM   Subscribe

How far do you have to transport a field mouse before it's not going to find its way back?

My sister lives in the country and has field mice that get into her house. She is tenderhearted and doesn't want to hurt them. So for years she has been keeping a live trap in a drawer in her kitchen. The mice like cheap store-bought chocolate chip cookies.

She catches the mice and takes them in the trap and lets them loose. In the winter, it's dark when she goes to work. So she lets them out at the park&ride where she catches the bus into town.

During the spring and summer, she only takes them to the edge of her property (5 acres) and lets them out at the end of her driveway.

I'm convinced that when the mice are most active, she's just giving them cookies, taking them for a ride and they're back home before she is.

There's a lot of them. She figures about 250 a year. A couple every three days.

How far do you have to take a field mouse for a ride before you aren't going to see that little bugger again? I suggested little buckets of cement for them to put their feet in, but she's not having any.
posted by warbaby to Pets & Animals (21 answers total) 3 users marked this as a favorite
Have her put a dab of nail polish or something on the backs of the mice before she releases them. If she's catching mice that have paint on them, she's not driving far enough. Otherwise, there's just a lot of mice. My guess is that she won't find any with paint on them, but if she does, have her start driving .1 mi farther each time. When she stops finding mice with paint - that's how far you have to drive.
posted by sanko at 9:08 PM on May 19, 2011 [5 favorites]

A daub of food coloring might be a bit better.
posted by elsietheeel at 9:15 PM on May 19, 2011

Farther than you'd think. 5 acres is definitely not far enough. 5 miles would probably be fine.
posted by geegollygosh at 9:16 PM on May 19, 2011

Thus sayeth the Great and Powerful Wikipedia:

Although these animals tend to live close together, they are aggressive towards one other.....The meadow vole* is so strongly attracted to areas of dense plant cover that even the presence of the scent of a predator will not discourage the meadow voles from remaining in that area.....Average females have between one and five litters in a year, producing about five pups in each litter.

I take this to mean that if the area around your sister's house is irresistible to the critters they will create a vast population in a small zone and will keep staying until the vegetation is removed.

At a capture rate of 250/year she may not be seeing the same ones.

* closest match for "field mouse"
posted by trinity8-director at 9:19 PM on May 19, 2011

I tried to talk her into marking them with food coloring, but she's resisting. She just wants an answer and not a project. I held my tongue about her mouse snacks and ride program being a project: she is my older sister...

Her property is wooded and very dense underbrush - like most of the Pacific Northwest. It's vole heaven.

Interestingly, neither of her two somewhat tamed feral cats seem to catch mice. A previous cat would frequently lay out a row of 2 to 4 dead mice just in case anybody needed a snack. Rabbits, too, but usually we'd only find the ears or a gall bladder.
posted by warbaby at 9:37 PM on May 19, 2011

It looks like may be a couple articles that would answer the question but my university's subscription doesn't go back far enough.

Check out:
Activity and Home Range of the Field Mouse, Microtus Pennsylvanicus Pennsylvanicus
W. J. Hamilton, Jr.
Vol. 18, No. 2 (Apr., 1937), pp. 255-263

Home Ranges and Populations of the Meadow Vole in Southern Michigan
W. Frank Blair
The Journal of Wildlife Management
Vol. 4, No. 2 (Apr., 1940), pp. 149-161

If you know the average home range of a mouse, you could maybe assume that if the human home is within the home range, the mouse will return; otherwise you're/your sister is safe.

But! If she wants to be super nerdy (and who doesn't?), she could mark them with hair dye or ear notches (marked so as to distinguish among individuals, of course) and then see if anyone shows up again. I'm guessing with that with 250 individuals/year you're looking at replacement rather than the same ones showing up and being caught again*. Anyway, if you know what your recapture rate is you can just apply some fancy stats and get your survival rate and population size. And then your sister can be horrified at the number of mice she is supporting (the cookies are probably only the tip of the iceberg).

*mathematically wouldn't the rate of being caught again be less than mating and your offspring being caught? So you have a 1/100 chance of being caught, then getting caught again you'd have another 1/100 chance for a total of 1/10000 of being caught twice. But if you have 10 offspring the odds decrease to 1/10 of one of them being caught therefore you're much more likely to catch an offspring of the original mouse that the same mouse again (not to mention that mice don't live very long at all and reproduce much faster than 10/litter/year). I don't guarantee my math here.
posted by hydrobatidae at 10:10 PM on May 19, 2011 [1 favorite]

I had the same question a few years back when using live traps to deal with a fairly ridiculous quantity of mice. At one point I caught 7 of the little bastards in the space of about two hours. I'd hear the little door snap shut, take the mouse a half mile down to the end of the road, and be settling back in at the computer just in time to hear the trap go again.

If they were really all different mice, or just a couple of incredibly energetic, determined, and not-very-bright mice, I never figured out.

Where I was going with this narrative, though, is that the next day I noticed a crack under the laundry room door, and then realized that the drier vent was open to the outside. We put a towel under the door and instantly stopped having mouse problems. Maybe your sister could more profitably spend the research time on looking around for mouse vulnerabilities in her house?

Not that I want to discourage any Science that might be happening here...
posted by brennen at 10:41 PM on May 19, 2011

I know she doesn't want to do the experiment, but there was another mouse question once where I mentioned trying to figure this out and my experience was that a few long blocks was sufficient. An actual biologist checked in and said its not very far (you have to read the earlier comments really for this to make sense). To attempt to answer your question directly, its hard to say just by acres, but google says the distance I used to take them was about 2500 feet, and I never saw a painted mouse again after letting it go.
posted by jeb at 10:45 PM on May 19, 2011 [1 favorite]

They will find their way back unless you sing "Born Free" while releasing them.

It especially helps if you are releasing them several miles from where you caught them.

In my experience.
posted by Snarl Furillo at 11:07 PM on May 19, 2011 [8 favorites]

Figuring out the distance is going to be hard, because you don't know what led them to her house - have they left scent marks, or are they from around a very short distance. Field mice can range in areas as large as a couple of square miles. Honestly, it's probably a lot more realistic for her to secure her house against the invasions in the first place, although to be fair, that won't be super easy - mice will find incredibly small spaces to squeeze through, and they also gnaw through a lot. But depending on the house, it may make sense to systematically close off all avenues of entry. Then it won't matter how far she drops off the ones trapped inside.
posted by VikingSword at 11:23 PM on May 19, 2011

I was going to say "heaven," but I see she's being humane about this.

Your sister needs to seal up the house, because who cares if they're the same mice or just an enormous extended mouse family all looking for long evicted Great Uncle Ned?

A mouse release every two or three days is too much, even in the country.

If she won't or can't seal the house, she needs a barn cat who can kill the mice without any remorse.
posted by bilabial at 4:34 AM on May 20, 2011

Field mice can range in areas as large as a couple of square miles.
What? That is patently absurd. The range of nesting rodents can be measured in feet. However, the range isn't the question, the question concerns their ability to home which is going to be a LOT father than their natural range. More reading if interested The short version is that a mouse can almost certainly rehome if only displaced by a few acres.
posted by Lame_username at 6:16 AM on May 20, 2011

And while I'm raining on parades, releasing a mouse far away to prevent them from rehoming is probably going to fatal in nearly every case. They need to be near humans, they are really not great competitors and they get shocked pretty easily. You can easily make a case that a quick death is more humane.
posted by Lame_username at 6:23 AM on May 20, 2011

Sorry to post repeatedly, but I realize you may not be able to read jstor. Mice can rehome over 2,000 meters (sometimes within 24 hours). They can cross rivers and other significant terrain features to do so and will pass through optimal habitat to return. At ranges of 2,000 meters, you started to see nearly half of them fail to make it, so I guess that implies that you are starting to get to the edge of what they are capable of. But that is more than a mile, which is pretty impressive when you think about it.
posted by Lame_username at 6:37 AM on May 20, 2011 [1 favorite]

We're pretty sure that the mice are getting in around the pipes in the wall coming into the kitchen sink. It's an area that can't be reached to seal, otherwise it could be plugged with copper mesh. We've tried expanding foam in a can, but they seem to be gnawing through it.

It's a rural area with section roads every mile, so the answer seems to be a section mile or two.

Damn if I know why the cats are so lazy. They are very efficient at killing a dish of food.
posted by warbaby at 7:17 AM on May 20, 2011

At 250 captured mice a year, sister's got more worries than how far before they come back. I'll be the dissenting voice here and suggest More Aggressive Steps than driving them down the road and letting them go.

I'll also argue that taking a creature at the bottom of the foodchain thousands of feet away from the place its known its entire life, far away from its nest-mates and known food source and general knowledge of available predators (none, inside the house, until a monster black snake finds the unlimited supply of food) and dropping it off in a place where it can't even sniff its way to a friendly hole (mice aren't exactly friendly to each other in the wild), and doing so in the daylight (cuz that's when sister's up, right?) is probably about as far away from "Humane" as I can imagine.

"Die where I don't have to see" is != to "Now you're safe!"
posted by TomMelee at 7:26 AM on May 20, 2011 [5 favorites]

I am sure that using a Sharpie or such marker would be much easier that trying to paint their little tiny nails. [said with tongue firmly planted in cheek]

In addition, the cats aren't lazy, they are tired and bored with all the prey.
posted by Drasher at 11:03 AM on May 20, 2011 [1 favorite]

Sounds like the house needs some sealing up, perhaps some foundation repairs?
posted by dhartung at 2:23 PM on May 20, 2011

I just want to note that acres are a measurement of area, so telling us that she goes to the edge of her 5-acre property isn't telling us anything at all.

If my property is three yards across and a hundred yards long, it's 300 square yards, but I can take a mouse to the edge of it in one stride.
posted by AmbroseChapel at 3:39 PM on May 20, 2011

Nthing the mighty-hunter barn cat suggestion (a very different animal than the current indoor-outdoor kitties) or a black snake, whose eyes will probably light up with delight at dusk on his/her first night at your sister's place. Tenderhearted though she may be, the cookied & rehomed mice may not be meeting a pleasant fate post-roadtrip.

I'd suggest getting this charming book for her, but it will probably make her even more likely to put out cookies.
posted by muirne81 at 12:35 PM on May 26, 2011

Another reference which might be helpful for you, the record distance (on a wheel) for wild mice is 18.5 miles in one day. Obviously they don't all run that all the time, but down the driveway? The distance by itself is nothing for them.
posted by anaelith at 10:51 AM on May 27, 2011

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